The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Various methods of controlling airbag deployment are previously known.
Reference Patent Document 1 describes an airbag apparatus to be designed for easy manufacture and to provide a deployment process that is simple to control. To achieve these ends, the airbag and inflator are installed within a retainer case, and when the inflator ignites and emits the gas into the airbag as a result of the vehicle experiencing a sudden shock, a door opens from the pressure of the inflating and deploying airbag. A deployment interference part that interferes with deployment of the airbag, and a runoff part from which the interference is relieved, are provided on the external side of the airbag in order to control the deployment of the airbag. The deploying airbag escapes from the deployment interference part as deployment of the airbag progresses. In this apparatus, the deployment interference part comprises a strap whose both ends are structured as fixed parts respectively.
Reference Patent Document 2 describes an airbag apparatus that, in order to equalize contact friction generated between the airbag and the interior members when the airbag deploys, provides a structure in which a folded up airbag is installed within an airbag module located in the vehicle's instrument panel. One end of an intervenient fabric part is fixedly attached at the securing part of the airbag to the airbag module, and the other end is free and non-fixed. This structure accomplishes a smooth airbag deployment action under a constant friction at the time when the airbag door is forced open by the deploying airbag even though friction is generated by contacting the airbag with the vehicle door or windshield, since the intervenient fabric part is put there between. In this apparatus, the fixed end of the intervenient fabric part is secured in the proximity of the hinge on the airbag door.
Reference Patent Document 3 describes an airbag apparatus that uses an improved method of altering the initial deployment direction of an airbag with the purpose of reducing the pressure applied by the deploying airbag to the passenger in the vehicle. To do this, the airbag apparatus has a structure comprising an airbag, a first frictional member, and a second frictional member. This structure has a portion contacting with at least a part of the airbag, and as a result of the second frictional member being laid over the first frictional member, friction is generated between the first and second frictional members when the airbag initially deploys. Frictional contact with the first frictional member is maintained while the airbag deploys in the lateral direction (in relation to the vehicle's passengers) until the point is reached where the friction is completely overcome by the deploying airbag.
Reference Patent Document 4 describes an airbag apparatus designed to prevent an airbag that initially deploys at high speed from interfering with a vehicle passenger or child seat. In this apparatus, a folded airbag is installed within the steering wheel module cover, and the edge of the airbag opening part is fixedly attached to a retainer part that supports the inflator. A deployment restrictor sheet is provided along the internal surface of the module cover, said restrictor sheet being fixedly attached to the retainer part with one edge thereof and covering the folded airbag in a direction extending from the rear to the front of the vehicle. The restrictor sheet is formed to a length greater than an inner periphery length of the module cover in the vehicle fore-aft direction. Airbag deployment, which occurs in direction moving toward the rear of the vehicle, is controlled by the restrictor sheet in a way that prevents the airbag from immediately contacting the passenger during initial deployment. In this airbag apparatus, similar to the one described by Patent Reference Document 2, the fixed part of the deployment restrictor sheet is secured in the vicinity of the lid hinge.    [Patent Reference Document 1] Japanese unexamined patent publication No. 2001-30863    [Patent Reference Document 2] Japanese unexamined patent publication No. 08-108816    [Patent Reference Document 3] Japanese unexamined patent publication No. 2007-22523    [Patent Reference Document 4] Japanese unexamined patent publication No. 2001-334900
One of the problems associated with the deployment of an automotive airbag is to restrain the force of deployment when the vehicle occupant is not in a correct position amenable to safe restraint by the deploying airbag. The incorrect position means, for example, that the occupant head or chest is contacted with or located in the vicinity of the airbag door. In this case it is desirable for the open force of the airbag door be restrained to the extent that it will not cause injury to the vehicle occupant should it strike the head, chest, or other body part during initial airbag deployment. Conversely, to avoid injury to the vehicle occupant resulting from a collision, an airbag must apply sufficient restraining force to safely hold the occupant when that occupant is seated in a correct position amenable to safe airbag restraint. It is desirable that an airbag be able to fulfill both of these tasks.
Because the airbag apparatus described in Patent Reference Document 1 places a strap around the airbag with both ends of the strap fixed, we can expect a reduction in deployment shock to a person in the incorrect position for airbag restraint. However, we cannot deny that this structure reduces the speed of deployment, and thus makes it difficult to obtain adequate performance from the airbag in respect to a vehicle occupant in a correctly seated position.
The airbag apparatuses described in Patent Reference Documents 2 and 4, which respectively utilize the intervenient fabric part or the restrictor sheet placed between airbag and interior member or between airbag and occupant, locate the fixed edge of said fabric part or sheet in the vicinity of the hinge on the airbag door for a smooth motion thereof. Considering the deployment of the airbag with the occupant in a less than correct position, this type of structure is unable to dampen the shock of initial deployment due to the difficulty of controlling the initial opening movement of the airbag door.
While we can expect the airbag apparatus described by Patent Reference Document 3 to reduce the force applied by an airbag to a vehicle occupant by controlling the direction of initial airbag deployment, there is a possibility that the friction generated between the first and second frictional members may cause said members to tear. Moreover, while this structure may dampen the shock of an airbag deploying when the vehicle occupant is in a less than correct position, there remains a problem in that the friction prevents airbag from deploying with sufficient velocity to safely restrain a vehicle occupant in the correct seating position.
As means of mitigating the aforesaid shortcomings, the automotive airbag apparatus invention described by this application is able to dampen airbag deployment pressure as means of avoiding injury to a vehicle occupant who has assumed a less than correct position in relation to the airbag, but is also able to deploy with sufficient velocity to safely restrain a vehicle occupant in a correctly seated position.